It is known, in particular from the French patent published under the No. 2 470 275 in the name of the Applicant, that a clamping collar can be provided with an undulation that provides a reserve of resilience.
French patent application No. 93 06 046 filed by the Applicant on May 19, 1993 proposes an improvement to a collar of that type.
That application discloses a clamping collar constituted by a rolled-up first metal strip portion referred to as an "inner" portion and having two radial folds in the vicinity of one of its ends forming a "lug", and by a second strip portion referred to as an "outer" portion, which is fixed at its first end to the outside face of the inner portion, which has an undulation forming a reserve of resilience, which is provided at its second end with a hook suitable for engaging behind the lug while the collar is being clamped, and which includes an "intermediate" part situated between the undulation and the hook and extending substantially along the periphery of the inner portion which thus has, in the vicinity of the other one of its ends, a covered zone covered by said intermediate part.
It is known that the reserve of resilience makes it possible to maintain satisfactory clamping even when the dimensions of the object to be clamped change, in particular under the effect of temperature variations.
The improvement provided by patent application No. 93 06 046 relates to avoiding discontinuity in the pressure applied by the collar on the object to be clamped when the inner strip portion is rolled up through more than 360.degree., i.e. when its two ends overlap.
However, in certain difficult cases, the qualities of the collars described in the above-specified documents can be lost while the collar is being installed or is being clamped.
More precisely, it can happen that while the hook is being engaged on the lug, the collar is inadvertently clamped too tight, and even if only temporary that runs the risk of causing the elastic limit of the metal to be exceeded locally.
Nevertheless, it turns out to be important for the collar to retain its elasticity so as to be able to continue guaranteeing clamping on the object to be clamped even if the dimensions of the object change slightly after the collar has been installed.
The patent application filed on May 19, 1993 by the Applicant under the No. 93 06 045 proposes providing the lug with an abutment member suitable for coming into abutment contact with the inside face of the hook while the hook is being engaged on the lug.
Overall that solution has proved satisfactory in preventing the elastic limit being exceeded around the collar, and more particularly in the region of the hook.
Nevertheless, the requirements laid down by manufacturers are such that it is essential, even in the most difficult of cases, to ensure total effectiveness of the reserve of resilience by avoiding the elastic limit being exceeded at all, specifically in that region.